Recently, buildings such as office buildings, restaurants, recreation facilities, factories, housings have substantially air-tight structures. Therefore, air stagnates in the buildings. Such air contains smoke floating in the air caused by tobacco, toner come out from a copy machine, particles of copy papers dust together with bad smell and often toxic substance therein. This impairs people in the buildings in health, and also makes the facilities and machines dirty. Due to this, the use of an electric dust collecting-type air cleaner has spread. Such cleaner is installed in the building to collect floating particles such as the smoke caused by tobacco and the toner, and remove offensive smells from the air.
Such air cleaner is shown in FIGS. 22 and 23. This air cleaner is of a wall-suspension type, and has a pre-filter 1, an electrostatic-type dust collecting unit 2, a deodorizing filter 3 made up of an active carbon fiber and the like, a fan 4 such as cross-flow fan and the like, and a power source (not shown).
In operation of the air cleaner, dirty air 5 containing, for example, floating particles such as the toner and the tobacco smoke is sucked into an inner portion of the air cleaner from a suction opening 6 near ceiling by a suction power of the fan 4. The dirty air 5 first passes through the pre-filter 1 to thereby lose relatively large ones of the floating particles. Subsequently, it flows into the dust collecting unit 2 where the floating particles are charged as a corona electrification and collected in electrostatically. Finally, the air flows into the deodorizing filter 3 to have its bad odors removed, and is then purified. The purified air 7 then blows toward a floor from a blowing opening 8 under the influence of a discharging power of fan 4. In the case of the air cleaner, the suction opening 6 is projected from a body of the air cleaner. Therefore, it is possible to circulate the air in a room effectively, so that the air is purified for a relatively short period of time.
Referring to FIGS. 24 to 26, the dust collecting unit 2 which is a major part of the air cleaner will now be described.
FIG. 24 is a vertical sectional view of the dust collector 2 shown in FIG. 26. FIG. 25 is a vertical sectional exploded view of the same dust collector 2 divided into two sub-units. FIG. 26 is a perspective view of the dust collector 2, illustrating a front side (i.e., air suction side) of the dust collector 2.
The dust collector 2 described above comprises a male sub-unit 11 having needle deflection electrodes 10 as a needle-attached prism structure arranged inside an outer casing-like frame 9; and, a female sub-unit 14 having collector cells (collector electrodes) 13 each assuming a rectangular pipe shape, wherein the shape has openings in its opposite ends, and the sub-unit 14 serves as an electrostatic dust collecting filter assuming a multiple grating shape, and is disposed inside an inner casing-like frame 12. With the frames 9 and 12 combined with each other, the collector cells 13 and corresponding needle deflection coupled electrodes 10 are oppositely disposed from each other. In other words, the needle deflection coupled electrode 10 is fixedly mounted in the corresponding collector cell 13, and spaced apart therefrom. It is noted that the male sub-unit 11 and the female sub-unit 14 are detachable from each other to facilitate cleaning work and the like thereof (see FIG. 25).
The needle deflection coupled electrode 10 is constructed of: a needle electrode 15 for generating an ionized space area to charge the floating particles passed therethrough; and, a prism-shaped deflection electrode (for example, approximately 10 mm square in cross-section, with a length of from 5 to 6 cm) 16 assuming a rectangular pipe-like shape having a front plate portion and a side plate portion, wherein the front plate portion fixedly supports the needle electrode 15, and deflects the floating particles (which have been charged by a potential of the side plate portion) to the collector cells 13. The needle deflection coupled electrodes 10 are connected with each other through metal coupling members 17 to have the same potential. On the other hand, these members 17 are supported by the outer casing-like frame 9 through insulating joint plates 18, 13 for electrically insulating the members 17 from the frame 9. It is noted that a high voltage (for example, 5 to 6 kV) is applied between the needle deflection coupled electrode 10 and the collector cell 13 during operation from a direct current high voltage power source (not shown) so that the needle deflection coupled electrode 10 has a positive potential while the collector cell 13 has a negative potential.
FIG. 27 is a schematic diagram illustrating the operation of the air cleaner. As described above in construction, when a direct current high voltage is applied to the needle deflection coupled electrode 10, a corona discharge occurs around a needle point of needle electrode 15 to form a continuous and stable ionized space area 19. At this time, the dirty air 5 sucked into the dust collecting unit 2 by the fan 4 passes through the ionized space area 19. In the area 19, oxygen having a low energy becomes first a positive ion. The positive ion then adheres to particles 20 in gases such as tobacco smoke to give a positive ion electric charge to the particles 20. When the particles 20 having the electric charge pass between a deflection electrode 16 and the collector cell 13, the particles 20 near the collector cell 13 adhere to the collector cell 13 having the negative potential. On the other hand, the particles 20 far apart from collector cell 13 are repelled by the deflection electrode 16 toward the collector cell 13 and then adhere thereto under the influence of the positive potential of the deflection electrode 16, so that the particles 20 having a micro-size of from 0.01 to 10 .mu.m are collected effectively.
FIG. 28(a) is a perspective view of a pin member 150 assuming a record player's stylus-like shape and made of stainless steel, wherein the pin member 150 was used as the needle electrode 15. Also, the deflection electrode 16 is comprised of a pair of bent metal plate members 160. The member 160 has: a pair of side plate portions forming in cross-section a U-shaped groove; and, a front plate portion connecting the side plate portions to form a U-shaped form in plan view. As a result, the pair of bent metal plate members 160 form a rectangularly hollow longitudinal portion, as shown in FIG. 28(b).
Referring to FIG. 28(b), a proximal end of the pin member 150 is attached to an abutting portion of the front plate portion of the bent metal plate member 160, and then fixed thereto using a silver solder G to form the needle deflection coupled electrode 10. However, since the dust collector 2 has 50 to 200 pieces of the needle deflection coupled electrodes 10, much time and labor are required to produce the needle deflection coupled electrodes 10 with the use of the silver solder G. Consequently, the air cleaner is high in manufacturing cost and low in productivity. In addition, the needle electrode 15 is connected with the abutting portion of the front plate portion through a butt joint, which is unstable in operation to offer a disadvantage.